blind alley is a noun meaning "a street with only one way in or out". It carries 2 recorded senses.
a street with only one way in or out
(figurative) a course of action that is unproductive and offers no hope of improvement
“all the clues led the police into blind alleys”
“so far every road that we've been down has turned out to be a blind alley”
trope
Definitions, synonyms and semantic relations for blind alley come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.